In a traditional MRI device, gradient coils are located within the main magnetic field. Due to the existence of the alternating current in the gradient coils, electrified wires in the gradient coils are subject to the Lorentz force according to the left-hand law of electromagnetism. Due to the existence of the alternating current, the force of the electrified wires in the gradient coils alter correspondingly. That may lead to violent vibrations which in turn may cause noise during a gradient switch. The transmission of the noise can be achieved through two means: air and structural components. In the airborne transmission, air surrounding the gradient coils can propagate the vibrations to adjacent components, for example, the shell of the MRI device. In the structure-borne transmission, vibrations generated in the gradient coils are sent to other nearby components through structural components. The structural components used herein may include different kinds of components contacting the gradient coils including, for example, a magnet, body coils, a shell, etc.
In a traditional MRI system, vibration sources (for example, gradient coils) are sealed in a vacuum environment, in order to decrease the noise transmission from within the MRI system. However, the conventional shimming cannot be performed while the gradient coils are sealed in the vacuum environment. Therefore, vacuum operations of the gradient coils are usually performed after shimming in a non-vacuum environment. Equipment for vacuum operations and operators may be needed for the initial installation of the MRI device. Additionally, vacuum operations are needed after every shimming maintenance, which takes extra time and resources.